1. Field of the Invention
The present invention relates to a proximity detector having an oscillating circuit which generates cyclically an unsustained pseudo-oscillation.
2. Description of the Prior Art
Such a proximity detector is described in the French patent application FR No. 86 13359 of Sept. 19th 1986 and includes an oscillating circuit having a capacitor and a coil which is influenced by an object to be detected. The oscillating circuit is connected to an energy source through a static switch driven by control pulses generated by a processing circuit including more particularly a comparator and a logic circuit.
Depending on whether the switch is closed or open and as a function of the state of the control pulses, the oscillating circuit is charged or respectively discharged. During pseudo-oscillation for discharging the oscillating circuit, a comparator compares its relaxation voltage with a threshold so as to generate measurement pulses which are representative of the proximity of an electrically conducting object and which are transmitted to the logic circuit for processing thereby.
This proximity detector has the advantage of making it possible to detect even very close objects while facilitating direct processing in digital form of the analog proximity information.
It seems however desirable to reduce the consumption of an inductive proximity detector of the type described so as to be able to construct its processing circuit in integrated circuit form, particularly using MOS technology. In addition, it would be advantageous to be able to correct in such a detector the dispersion and variations affecting the characteristics of the oscillating circuit particularly the inductances of the coils. The purpose of the invention is more particularly to respond to these requirements in a proximity detector of the above mentioned type.